Computers and mobile telephony devices that communicate via wireless networks (also referred to herein as mobile networks) include a physical subscriber identity module (SIM) card. The SIM card securely stores the service-subscriber key, also known as an International Mobile Subscriber Identifier (IMSI), which is assigned by the wireless service provider when service is activated. The SIM card also stores an authentication key that is used by the mobile device to access the device's home mobile network. Currently the service provider must issue a physical SIM card to the mobile device user before service can be activated.
The physical SIM card is tied to the issuing service provider and home network. Each location area of a public land mobile network (PLMN) has a unique identifier which is known as a Location Area Identity (LAI). The Location Area Identity includes a Mobile Country Code (MCC), Mobile Network Code (MNC), and Location Area Code. Base stations in a given mobile network transmit the LAI of the area in the Broadcast Control Channel (BCCH).
The mobile networks with which a given mobile device can communicate are stored in the SIM in various different lists, such as a list of Equivalent Home PLMN (EHPLMN), which provides information about cells within the home network location area, or in user controlled or operator controlled PLMN selector lists that are used to determine which network should be selected. During network registration, the mobile device selects a mobile network from the available PLMNs in its current location. The automatic selection procedure searches the lists of available PLMNs to find a suitable PLMN in accordance with 3GPP specifications TS 23.122, which is available at the URL www-3gpp-org/ftp/Specs/html-info/23122-htm, where the URL has been modified to replace the ‘.’ character with a ‘-’ character to avoid an active hyperlink from within this document. If a suitable match is found, the mobile device registers to the selected PLMN as a home network.
When a mobile device attempts to access a mobile network, the physical SIM card provides the authentication key that is associated with the home network. If the mobile device is outside the home network area, a partner network service provider requests authentication credentials from the home network service provider in order to authorize the mobile device to access the wireless network. The partner service provider imposes “roaming charges” for access to the partner mobile network. To avoid roaming charges, a mobile device user can obtain another physical SIM card for areas to which the user of the mobile device frequently travels, and then switch physical SIM cards when traveling to that area.